Nippon Telegraph and Telephone Corporation

Kenji Sato

Yutaka Miyamoto

Akira Hirano

Kazushige Yonenaga

Takuya Ohara

Hiroji Masuda

Kunihiko Mori

Masaki Asobe

Akihiko Matsuura

Hiromu Toba

An inline repeater that uses a forward-pumped DRA that can use a pumping light source such as an FBG pumping light source and a fiber laser, which are the most commonly used, and an optical fiber communication system are realized. The optical fiber communication system comprises silica fiber as a gain medium for Raman amplification to amplify a signal light; a pumping light source that emits a pumping light that co-propagates through the silica fiber in the same direction as the signal light; and a multiplexer disposed between the silica fiber and the pumping light source that multiplexes the signal light and the pumping light, with the multiplexer being provided with a means to multiplex the signal light input thereto having a wavelength longer than the zero-dispersion wavelength of the silica fiber and the pumping light emitted from the pumping light source, and the pumping light source being equipped with a means to emit pumping light, with the longest wavelength of the pumping light being shorter than the shortest wavelength of the signal light by a frequency difference on the low-frequency side of 13.7 to 30 THz.

Inline repeater and optical fiber communication system

A mode-locked laser serves as a light source for stabilizing the frequency of each optical carrier and generates high-quality optical multi-carrier. The mode-locked laser is equipped with a master laser for generating master laser light; a mode-locked laser section including in an optical resonator at least a modulating section, am amplifying section, and a bandwidth limiting section for reducing mode partition noise; and a signal generating section for generating a periodic signal that serves for mode locking of the mode-locked laser section and is to be applied to the modulating section. The master laser light is input to the optical resonator of the mode-locked laser section to cause injection locking. An optical multi-carrier source is constructed by combining this mode-locked laser with a waveguided optical nonlinear medium.

Mode-locked laser and optical multi-carrier source using same

A system which improves wavelength tolerance, compensates dispersion in a simple way, reduces limitation of the fiber input power is disclosed. The operation includes receiving a clock signal from a system clock source; modulating a single mode optical signal based on the clock signal and generating an optical pulse signal having two longitudinal modes, the frequency interval thereof being n&#xd7;B, n being a natural number and B being a transmission speed; generating a partial response signal by converting a binary NRZ signal from a digital signal source in synchronism with the system clock source; and modulating the optical pulse signal based on the partial response signal, and outputting a binary RZ modulated signal. The binary RZ modulated signal is input into a receiver, where two partial response components in the optical spectra of the input signal are divided, and one or both of the components are received.

Optical transmission method, optical transmitter, optical receiver, and optical transmission system

An optical transmitter for realizing a high tolerance with respect to the group velocity dispersion of the optical fibers, a small receiver sensitivity degradation, and an improved stability that is hardly affected by the group velocity dispersion even in the case of network scale expansion, is constructed by a light source section for generating optical clock pulses synchronized with a signal bit rate while maintaining a duty ratio of the optical clock pulses constant, which is capable of variably setting the duty ratio, and an encoding section for encoding the optical clock pulses by using electric signals synchronized with the optical clock pulses while setting a relative optical phase difference between the optical clock pulses in adjacent time-slots to be an odd integer multiple of &pgr;.

Growing community of inventors

Yokosuka, Japan

Kenji Sato